Experimental investigation of the heat transfer performance of an oscillating heat pipe with LiCl salt solution

Abstract

The heat transfer performance of oscillating heat pipes (OHPs) with LiCl solution was investigated experimentally at the concentration of 5wt%, 10wt% and 15wt% with the heat input ranging from 10 to 100 W and the filling ratio (FR) of 45%, 55%, 62%, 70%, 80%, and 90%. OHP with different concentrations of LiCl solution can improve the heat transfer performance compared with deionized water (DW) in most conditions, because of the combined positive effects of bubble characteristics, absorption and generation mechanism, two-phase flow, mass transfer, and other behaviors caused by hygroscopicity of LiCl solution. At an appropriate filling ratio (62% and 70%), the addition of LiCl in DW reduces the thermal resistance of OHP. The thermal resistance of a 62% volume of 10wt% LiCl solution reduces up to 61% compared with DW. At low filling ratio (45% and 55%), LiCl solution can reduce the temperature of the evaporation section and improve the anti-dry-out ability; simultaneously, the higher the concentration, the better the effect. It is due to the low water activity and the characteristics of bubble generation and growth in LiCl solution. At increased filling ratio (80% and 90%), the reduction of the gas phase space inside the OHP and the slowing down of the working fluid make the effect of adding LiCl less on the heat transfer performance, 5wt% LiCl solution performs better than the other concentrations.